Just some thoughts...

Would you really want to reflect the language of the time? It would be nearly unreadable, nearly un-understandable to modern day people. I've written a few shorts from the POV or earlier times and my language takes on a different rhythm, cadence, way of stating things. That seems to work well. It gives the flavor but keeps it totally readable and believable. It seems to come naturally to me so I'm not sure I can tell someone else how to do it.

It does sound like an interesting story. Even without the language problems, though, you're right; it'll take a lot of research into history, sociology, maybe even psychology.

How the child reacts as an adult to all this? Some of it would depend on the parents if he remembered them. What did they teach him by example? He could be someone who blesses his blessing of long life and chooses to do good, curses it and becomes an angry man who does nothing but hurt those around him, or becomes arrogant and sets himself up as a noble and later, perhaps a politician, someone who can control events and people around him.

Sorry, I'm a writer. Give me a synopsis and my mind takes off. I hope you do write it. I'd love to read it.